I have 5 AR's. One S&W Tactical, a Daniel Defense and 3 I built the way I wanted them. I got the S&W first. It was one of the VERY first ones they made. It is a rifle that pi**ed me to no end. Two trips back to the factory, a couple of telephone conversations with the "head" gunsmith, who talked down to me about the rifle. Finally he "done me a favor" and found and fixed what was wrong with the rifle. The barrel nut was only finger tight allowing short stroking when fired from a rest. The smith and all his helpers had no issues out of the rifle, after several rounds, however they were shooting it offhand not off a bench, allowing pressure to be against the barrel. I got a new barrel (Mossberg) and it was torqued down properly out of it. However, I still don't trust it as a "go to" rifle. Sorry to hijack the thread.

One weird thing about the replacement barrel...it has no caliber or twist rate markings at all on it. The smith said the barrel he put on it came from a run of AR's they were doing for Las Vegas SWAT at the time.